Hello everyone,

I've got a '97 850 (Base, Sedan) that doesn't seem to want to pass inspection.

Both my scanner at home and the scanner at the shop report the same thing- Catalytic, Evap, 2nd Sys, O2 Sensor (both heated & non-heated), and EGR System are all marked as not ready. The guy at the shop told me to drive it for 50 miles, and then come back. Thing is, I've driven it for more than 400 miles since it failed inspection; something that I'd imagine would be plenty of time for the monitors to reset. I don't have any Fault/Trouble codes reported from OBDII, only that the monitors are 'not ready.'

I've tried leaving the battery wires jumped to each other for a few hours, checked my ECU fuse, tried clearing any possible codes, tried doing the OBDII drive cycle, even replaced both O2 sensors, just about every solution I've seen while lurking around here, but I still can't get anything to work. I've done the PCV glove/balloon test over the oil cap, and that seemed fine as the glove wasn't filling up- only being sucked down slightly by the air pressure.

Any ideas?

 

Miles are irelevant. The car needs to go thru it's drive cycle.

https://www.ipdusa.com/techtips/1006...20the%20engine.

 

Yes , complete a drive cycle. The " Catalytic, Evap, 2nd Sys, O2 Sensor (both heated & non-heated), and EGR System are all marked as not ready." Those all require specific driving techniques to complete them quickly except for the heated O2, Those are checked when first starting. The cat and evap are at the end of the list. O2 sensors are tested before the cat, evap requires 17 minutes or so of steady state driving If I remember correctly, at less than x rpms with between 25% and 85% gas in the tank. Too low - won't test, too full, same thing, The car must have a certain number (7 I think) of times the throttle returns to idle and the idle switch works correctly,the car must idle for x seconds several times during the process. If you drive too fast, or slow or not long enough - those won't complete. It's been a while and those older cars were a bear sometimes to complete a cycle. What exactly are the drive cycle instructions you are following? I always drove with a scanner that would tell me when each completed.

Don't disconnect the battery - then you have to start all over!

This looks similar to what I followed to complete a cycle. Ac off, engine not warmed up.

http://volvospeed.com/vs_forum/topic...-instructions/

 

I've already tried the drive cycle, but I guess it couldn't hurt to try again. Is there anything else that might be causing it?

 

Follow the drive cycle progress with a scan tool as you drive, I've seen write ups where the exact order of completion is described. That may give you an idea of where it's getting hung up. Your O2 sensor heaters are usually checked when first started cold. It checks the current that is used by the heaters. You could go back and try to complete the hanging portion of the cycle until it passes.

Years ago my local dealer would offer to complete a drive cycle and get an e test for 2 hours labor time ($120 at the time) They would send a lower wage employee out with drive cycle instructions and a stop watch. - Sorry those early OBD cars were very difficult to complete their drive cycle. In GA they even issued a waiver for certain car Models (not only Volvos) that were difficult. If the cel was not on and no active codes, the 96-98 Volvos passed the e test.

If all the components are working - then it's possible the ECU has a problem. I'm not recommending that as a solution - in my business my techs would frequently claim control units were needed to solve problems - so I would get a used one and then they would find the real problem and I would return the used module.

 

So, last night I did a drive cycle. Instead of FuelSys1 being stuck in CL_Fault, it's now perpetually in OL_Fault. I was able to get it to report a DTC (with CEL) after roughly 40 minutes of driving at ~2k rpm, P0130. 2 of my 6 monitors stuck in Not Ready went to Ready.

From what I could gather, it potentially may be a bad O2 sensor connection, either a broken vacuum hose or a dirty/faulty MAF, does this sound correct?

 

O2 sensors have two circuits - one controls the heating element the second controls the feedback for the fuel trim (aka the lamda signal). Different codes will be set for open vs short circuits or an "out of range" signal. The P0130 is somewhat of a generic code which simply says the ECU is not seeing what its expecting from the O2 sensor (ie the voltage is out of range), meaning the ECU cant adjust the fuel trim enough to get the O2 sensor's signal back into a happy place. Check youtube for some vids on how to do some basic O2 sensor tests (you can disconnect it up on the firewall). As noted if the sensor appears good, other things that impact fuel trim (intake air leaks, throttle body or MAF issues etc) could be in play. You may need a smoke test to look for air leaks so see if your local shop will do that for you...

Have you tried watching the real time data with your code reader to see how the O2 sensor signal varies?

 

The O2 Sensors (both front and rear) are brand new. When I put them in I was getting a normal sine wave for the voltage, however while I was doing the drive cycle I noticed that it was at a flat ~0.48v. It sometimes went to 0.475, but it was rare and essentially negligible. Will try to do the O2 sensor test/check the connection, might clean the MAF too and see if that helps.

Anything else you could recommend?

 

Should be a sine wave from the front sensor all the time - the peaks become closer with higher rpms, so perhaps your Voltmeter just can't sample voltage fast enough to see them (unless you are using an oscilloscope)

The rear sensor voltage will still fluctuate, but should be more stable after the converter starts working, with voltage down near 0 (after the converter uses up the O2)

 

This makes me so glad i dont have to pass in my state... i have no cat and no down stream 02.

 

Wow; can't believe IPD would post bogus info like that on their site! The readiness monitors not resetting properly is (or should be) a very well known issue by now. See this post and read about it. Common issue for volvo early editions of OBD2 from MYs 1996-1998.
Convert daily driver 850 to 4.4 - Performance Modifications - Volvospeed Forums
Check out the links within above post too for more info.

OP: What are you measuring the O2 sensor output with? Assume it's a VOM? It's likely averaging the voltage as frequency increases.

The P0130 (I don't think) is related to your readiness resetting, but it does sound like you may have an vacuum leak, or at maybe an exhaust leak?
https://www.obd-codes.com/p0130

 

Just been watching the sensor output on my OBDII reader. After cleaning the MAF I noticed that the fuel economy and sour exhaust smell improved (likely no longer overburning fuel), though the monitors are still stuck. Guess the next thing I'm trying is poking around for any busted hoses.

Have any ideas for commonly broken vacuum/exhaust hoses?

 

OK a question - have you actually had a e test done? Or just your shop/testing station telling you it's not ready? (trying to be a nice guy since they think you will fail and waste your x dollars) In my state due to the fact that z year volvos (and other cars) won't complete a drive cycle easily - if there are no codes stored, the car gets a pass - and you get your registration.

 

No, haven't had the time. Every time they just tell me it's not ready, and to drive it some more so that the monitors will reset- even though that's total BS.

In Texas, if the car is 25 years or older it doesn't even require an emissions test.

 

Alright, so a quick update:

First, I apparently had my O2 Sensors backwards on which plug they were connected to. Weird, considering I replaced them one at a time, but the point is that now instead of a flat ~0.48v, it's an actual sine wave.

Second, I read on another forum post how someone's faulty ABS module tripped up their drive cycle. The first thing I did back when I bought the car was replace the dead module, and it passed just fine. In an attempt to replicate the condition, I unplugged the ABS module and drove for about 20 minutes up the road at 2k rpm. When I got back home, I plugged the module back in and found that 2 of the monitors had gone to ready.

I'm not sure if the ABS module had any bearing on it; it was likely the O2 sensors now producing useable data for the drive cycle. Either way, that's only 4 more monitors to go!

Will try the same route a couple times again tomorrow with the module plugged in.

[EDIT: 2/24/21]
Ran the route again today. One more monitor went ready, got a new DTC; P0136. From what I could gather it's an issue with the rear O2 sensor. Would there be any other small issues associated with the code?

 

An update since I'm still working at this. I've made a bit of progress, still have a ways to go though.

First, the good:

- I did what I should've done originally and bought a pair of Bosch sensors, and that got rid of my O2 sensor codes.
- I mentioned last time that I'd also clean the MAF, which produced slightly higher readings on its output, so I'm going to assume it was a probable contributing factor.
- My starter had gone out, so while removing the hoses connecting the engine to the airbox to get at it, I found this (see below) hose that was completely blown out. Sorry for the bad angle, but can anyone identify any small hoses down in that area? The hose that was normally there fits over a small tube, one of a pair that are seemingly attached. I replaced it with a spare hose I had lying around as well as a new O-ring for the plastic elbow that connected to it.
- I've gotten two more (5 total, better than the normal 3) of the monitors to stay consistently ready without any DTCs.


You can see bits of the blown-out hose that melted down where it normally should be.

Second, the bad:

- Instead of being stuck in CL-Fault, fuelsys1 is now trapped in OL-Drive, occasionally going into OL for a few seconds, but I've only seen it do it on a cold start.
- Something I might have overlooked in my previous data stream observances, both the short and long term fuel trim are stuck where they are, and won't change regardless of idle, gentle driving, WOT, etc. I read a page on MVS that mentioned an easy way to reset fuel trim values was to disconnect the battery and turn the key to on, but that's something I'll have to try tomorrow morning.
- I've done about three drive cycles so far, the first two times resulting in one more monitor going green. I think I might've started too hot on the third.

So, that's where I stand right now. Just four more monitors to go. If anyone has any more advice, I'm all ears.

 

Both pcv hoses wrap Around the side of the head right there next to the throttlebody

 

Good to know might look into replacing it in the future, though the spare hose I had seems to be making a good seal.

I did the capacitive discharge, and the fuel trim seems to be responding, which is good. Saw a noticeable bump in fuel mileage too. Now though, fuelsys1 is back to being stuck in CL_Fault, though it seems to be a bit more consistent with its behavior.
If RPM is between ~1.8k - 2.2k, and MPH is between ~15 - 45, fuelsys1 will report in CL. If either of these values exceed either limit, it trips into CL_Fault. When letting off the gas at high speed, it will enter OL_Drive. Yesterday when 5 (instead of the usual 3) monitors were green, it was just stuck in OL_Drive, only entering OL on a cold start, so I'm assuming it's mostly to do with the monitors still not being happy.

Did another drive cycle earlier, started at ~80 degrees farenheight, but no monitors wanted to switch. Any thoughts? I'm honestly considering calling up my local dealer to do the drive cycle at this point if I can't get it to cooperate.